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Finding benchmark brown dwarfs to probe the substellar initial mass function as a function of time
Using a simulated disc brown dwarf (BD) population, we find that newlarge area infrared surveys are expected to identify enough BDs coveringwide enough mass-age ranges to potentially measure the present day massfunction down to ~0.03Msolar, and the BD formation historyout to 10Gyr, at a level that will be capable of establishing if BDformation follows star formation. We suggest these capabilities are bestrealized by spectroscopic calibration of BD properties (Teff,g and [M/H]) which when combined with a measured luminosity and anevolutionary model can give BD mass and age relatively independent of BDatmosphere models. Such calibration requires an empirical understandingof how BD spectra are affected by variations in these properties, andthus the identification and study of `benchmark BDs' whose age andcomposition can be established independently.We identify the best sources of benchmark BDs as young open clustermembers, moving group members, and wide (>1000au) BD companions toboth subgiant stars and high-mass white dwarfs (WDs). To accuratelyasses the likely number of wide companion BDs available, we haveconstrained the wide L dwarf companion fraction using the 2-Micron AllSky Survey (2MASS), and find a companion fraction of2.7+0.7-0.5percent for separations of~1000-5000au. This equates to a BD companion fraction of34+9-6percent if one assumes an α~ 1companion mass function. Using this BD companion fraction, we simulatepopulations of wide BD binaries, and estimate that80+21-14 subgiant-BD binaries, and50+13-10 benchmark WD-BD binaries could beidentified using current and new facilities. The WD-BD binaries shouldall be identifiable using the Large Area Survey component of the UnitedKingdom Infrared Telescope (UKIRT) Infrared Deep Sky Survey, combinedwith the Sloan Digital Sky Survey. Discovery of the subgiant-BD binarieswill require a near-infrared imaging campaign around a large (~900)sample of Hipparcos subgiants. If identified, spectral studies of thesebenchmark BD populations could reveal the spectral sensitivities acrossthe Teff, g and [M/H] space probed by new surveys.
| Revisiting the population of Galactic open clusters
We present results of a study of the galactic open cluster populationbased on the all-sky catalogue ASCC-2.5 (I/280A) compiled from Tycho-2,Hipparcos and other catalogues. The sample of optical clusters fromASCC-2.5 is complete up to about 850 pc from the Sun. The symmetry planeof the clusters' distribution is determined to be at Z_0=-22±4pc, and the scale height of open clusters is only 56±3 pc. Thetotal surface density and volume density in the symmetry plane areΣ= 114 kpc-2 and D(Z_0)=1015 kpc-3,respectively. We find the total number of open clusters in the Galacticdisk to be of order of 105 at present. Fluctuations in thespatial and velocity distributions are attributed to the existence offour open cluster complexes (OCCs) of different ages containing up to afew tens of clusters. Members in an OCC show the same kinematicbehaviour, and a narrow age spread. We find, that the youngest clustercomplex, OCC 1 (log t<7.9), with 19 deg inclination to the Galacticplane, is apparently a signature of Gould's Belt. The most abundant OCC2 complex has moderate age (log t≈8.45). The clusters of thePerseus-Auriga group, having the same age as OCC 2, but differentkinematics are seen in breaks between Perseus-Auriga clouds. The oldest(log t≈8.85) and sparsest group was identified due to a large motionin the Galactic anticentre direction. Formation rate and lifetime ofopen clusters are found to be 0.23±0.03 kpc-2Myr-1 and 322±31 Myr, respectively. This implies atotal number of cluster generations in the history of the Galaxy between30 to 40. We estimate that less than about 10% of the total Galacticstellar disk population has ever passed an open cluster membership.
| Astrophysical parameters of Galactic open clusters
We present a catalogue of astrophysical data for 520 Galactic openclusters. These are the clusters for which at least three most probablemembers (18 on average) could be identified in the ASCC-2.5, a catalogueof stars based on the Tycho-2 observations from the Hipparcos mission.We applied homogeneous methods and algorithms to determine angular sizesof cluster cores and coronae, heliocentric distances, mean propermotions, mean radial velocities, and ages. For the first time we derivedistances for 200 clusters, radial velocities for 94 clusters, and agesof 196 clusters. This homogeneous new parameter set is compared withearlier determinations, where we find, in particular, that the angularsizes were systematically underestimated in the literature.
| Proper Motions of Open Star Clusters and the Rotation Rate of the Galaxy
The mean proper motions of 167 Galactic open clusters withradial-velocity measurements are computed from the data of the Tycho-2catalog using kinematic and photometric cluster membership criteria. Theresulting catalog is compared to the results of other studies. The newproper motions are used to infer the Galactic rotation rate at the solarcircle, which is found to be ω0=+24.6±0.8 km s-1 kpc-1.Analysis of the dependence of the dispersion of ω0 estimates onheliocentric velocity showed that even the proper motions of clusterswith distances r>3 kpc contain enough useful information to be usedin kinematic studies demonstrating that the determination of propermotions is quite justified even for very distant clusters.
| Radio Polarization from the Galactic Plane in Cygnus
We present 1420 MHz (λ=21 cm) observations of polarized emissionfrom an area of 117 deg2 in the Galactic plane in Cygnus,covering 82deg
| On the Galactic Disk Metallicity Distribution from Open Clusters. I. New Catalogs and Abundance Gradient
We have compiled two new open cluster catalogs. In the first one, thereare 119 objects with ages, distances, and metallicities available, whilein the second one, 144 objects have both absolute proper motion andradial velocity data, of which 45 clusters also have metallicity dataavailable. Taking advantage of the large number of objects included inour sample, we present an iron radial gradient of about -0.063+/-0.008dex kpc-1 from the first sample, which is quite consistentwith the most recent determination of the oxygen gradient from nebulaeand young stars, about -0.07 dex kpc-1. By dividing clustersinto age groups, we show that the iron gradient was steeper in the past,which is consistent with the recent result from Galactic planetarynebulae data, and also consistent with inside-out galactic diskformation scenarios. Based on the cluster sample, we also discuss themetallicity distribution, cluster kinematics, and space distribution. Adisk age-metallicity relation could be implied by those properties,although we cannot give conclusive result from the age- metallicitydiagram based on the current sample. More observations are needed formetal-poor clusters. From the second catalog, we have calculated thevelocity components in cylindrical coordinates with respect to theGalactic standard of rest for 144 open clusters. The velocitydispersions of the older clusters are larger than those of youngclusters, but they are all much smaller than that of the Galactic thickdisk stars.
| Searching for unknown open clusters in the Tycho-2 catalog
We present 11 new open cluster candidates found in a systematic searchfor unknown star clusters using the astrometric and photometric dataincluded in the Tycho 2 catalog. The possible existence of these stellaraggregates is supported by the analysis of proper motions,color-magnitude diagrams, stellar density distributions, and by thevisual inspection of the Digitized Sky Survey (DSS) plates. With thesetools we were able to determine mean absolute proper motions as well aspreliminary reddenings, distances and ages for the majority of thecandidates. We found that most of them are possibly nearby (closer than~ 600 pc) open clusters never studied before.Based on observations of the ESA Hipparcos satellite.Figures 1 and 2 are only available in electronic form athttp://www.edpsciences.org
| Physical parameters of the Algol system BP Muscae from simultaneous analysis of GENEVA 7-colour light curves
The semi-detached eclipsing binary system BP Muscae has been analysedusing the Wilson-Devinney program. Light curves have been obtained inthe GENEVA 7-colour photometric system, and radial velocity curves forboth components have been measured with the spectrograph CORALIE. Thephysical and orbital parameters have been determined through aself-consistent simultaneous solution of light curves in seven coloursand of the radial velocity curves of both components. The absoluteelements of the components are, for the primary (mass gainer),M1 = 2.40 +/- 0.01 Msun, R1 = 2.64 +/-0.01 Rsun, Mbol_1 = 0.66 +/- 0.04,Teff_1 = 9180 +/- 90 K, and for the secondary (mass loser),M2 = 0.68 +/- 0.01 Msun, R2 = 3.76Rsun, Mbol_2 = 2.40 +/- 0.08, Teff_2 =5160 +/- 90 K. The semi-major axis A of the relative orbit is 13.617 +/-0.019 Rsun. The spectral type of the components are A0.5/1.5V (primary) and about G5 III. The distance to BP Mus is evaluated as 562+/- 17 pc, and the colour excess E[B2-V1] as 0.220 +/- 0.014.Based on observations collected at the Swiss 70 cm and 120 cm telescopesat the European Southern Observatory (La Silla, Chile).Table 1 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/398/1073
| Urban Astronomy: Observing the Messier Objects from the City
Not Available
| Membership in the Region of the Double Cluster h and χ Persei Working from Proper Motions and Positions: Distance Moduli and Extinction in That Galactic Direction
A segregation between cluster members and field stars in the region ofthe double cluster h and χ Persei is accomplished working fromproper motions and positions as kinematic random variables. Theextinction RV and the distance moduli are determined once thephysical cluster members are found.
| A Highly Ordered Faraday Rotation Structure in the Interstellar Medium
We describe a Faraday rotation structure in the interstellar mediumdetected through polarimetric imaging at 1420 MHz from the CanadianGalactic Plane Survey (CGPS). The structure, at l=91.8d,b=-2.5d, has anextent of ~2°, within which polarization angle varies smoothly overa range of ~100°. Polarized intensity also varies smoothly, showinga central peak within an outer shell. This region is in sharp contrastto its surroundings, where low-level chaotic polarization structureoccurs on arcminute scales. The Faraday rotation structure has nocounterpart in radio total intensity and is unrelated to known objectsalong the line of sight, which include a Lynds Bright Nebula, LBN 416,and the star cluster M39 (NGC 7092). It is interpreted as a smoothenhancement of electron density. The absence of a counterpart, in eitheroptical emission or total intensity, establishes a lower limit to itsdistance. An upper limit is determined by the strong beam depolarizationin this direction. At a probable distance of 350+/-50 pc, the size ofthe object is 10 pc, the enhancement of electron density is 1.7cm-3, and the mass of ionized gas is 23 Msolar. Ithas a very smooth internal magnetic field of strength 3 μG, slightlyenhanced above the ambient field. G91.8-2.5 is the second such object tobe discovered in the CGPS, and it seems likely that such structures arecommon in the magneto-ionic medium.
| A Spectroscopic Search for λ Bootis and Other Peculiar A-Type Stars in Intermediate-Age Open Clusters
As part of our continuing search for peculiar A-type stars, especiallyλ Bootis stars, in open clusters of all ages, we have obtainedclassification spectra of 130 late B, A, and early F-type stars in 12intermediate-age open clusters, including NGC 1039, 2281, 2548, 6633,7039, 7063, 7092, and 7209, IC 4665, IC 4756, Stock 2, and Praesepe. Thespectra were obtained with resolutions of 1.8 and 3.6 Å on the 0.8m telescope of Appalachian State University and were classified on theMK system. Numerous classical Ap and Am stars were found among the 130,including two new Ap stars in NGC 7092. In addition, three emission-linestars and two candidate λ Bootis stars were found. Neither ofthese λ Bootis candidates turned out to be members of theirrespective clusters. Combined with 184 stars previously classified in 10other intermediate-age open clusters, also devoid of λ Bootisstars, a statistically significant null result is obtained. We discussthe implications of this null result for our understanding of theλ Bootis mechanism.
| Proper motions of open clusters based on the TYCHO2 Catalogue. II. Clusters farther than 1 kpc
We determined the mean absolute proper motion of 94 open clusterssituated farther than 1 kpc from the Sun. The results are derived fromthe stellar proper motion data given in the Tycho2 Catalogue. The meanproper motion of the clusters and membership probability of individualstars were obtained from the proper motion data by applying thestatistical method proposed by Sanders (\cite{Sanders1971}). Themeasurements made use of a large number of stars, usually several tens,for each cluster. The total number of stars investigated in the fieldsof the clusters is 4864 of which 2021 were considered members. For 55clusters, this is the first determination of the proper motion. Based onobservations of the ESA Hipparcos satellite. Tables 1 to 95 are onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/388/168
| The Pulsation Mode of the Cluster Cepheid V1726 Cygni
CCD V-band observations and archival O-C estimates are presented for the4.237 day Cepheid V1726 Cyg, which is a member of the open clusterC2128+488 (Anon. Platais), and the data are analyzed in conjunction withother available photometric data in order to study the star's periodvariations. An O-C analysis of the data yields the following improvedephemeris for the variable,HJDmax=2,444,020.5892+4.2369334E+2.044×10-8E2, which implies that the period of V1726 Cyg isincreasing at a rate of +0.304+/-0.026 s yr-1, consistentwith a star in the third crossing of the instability strip provided thatit is pulsating in the first-overtone, rather than fundamental, mode.Overtone pulsation for V1726 Cyg is also indicated by its low amplitude,sinusoidal light curve, and derived Fourier parameters, despitereservations about the significance of the latter. No evidence is foundfor random cycle-to-cycle variations in period for V1726 Cyg.
| NSV 25616 is a New Classical Cepheid
I report the investigation of a new classical Cepheid on Moscow archiveplates.
| Hipparcos Trigonometric Parallaxes and the Distance Scale for Open Star Clusters
Hipparcos trigonometric parallaxes are used to estimate the distances tothe maximum possible number of open star clusters (OSC); distance moduliare estimated for 45 clusters with maximum heliocentric distances ofabout 1000 pc. The latter value can serve as an estimate of the limit towhich it still makes sense to use Hipparcos trigonometric parallaxes todetermine the distances to small groups composed of 6-10 sufficientlybright stars. A systematic correction to the distance moduli of clustersfrom the homogeneous catalog of OSC parameters (Loktin et al. 1997,2000) is estimated, which turns out to be independent of the clusterage.
| Proper motions of open clusters within 1 kpc based on the TYCHO2 Catalogue
We present mean absolute proper motions of 112 open clusters, determinedusing the data from the Tycho2 Catalogue. For 28 clusters, this is thefirst determination of proper motion. The measurements made use of alarge number of stars (usually several tens) for each cluster. The totalnumber of stars studied in the fields of the 164 open clusters is 5016,of which 4006 were considered members. The mean proper motions of theclusters and membership probability of individual stars were obtainedfrom the proper motion data by applying the statistical method proposedby Sanders (\cite{Sanders71}). Based on observations of the ESAHipparcos satellite. Tables 1, 2 and 5 to 117 are only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/376/441
| A spectroscopic survey for lambda Bootis stars. III. Final results
In the third paper of a series dedicated to the spectroscopic survey fornew lambda Bootis stars, we present all new and confirmed members of thegroup as well as a detailed analysis of the observed sample. The natureof this small group of chemically peculiar stars of the upper mainsequence still challenges our understanding of processes like diffusion,mass-loss and accretion. The typical abundances pattern (nearly solarvalues for C, N, O and S whereas the Fe-peak elements are moderate tostrong underabundant) can still not be explained by any proposed theory.Hence, the significant increase of new members gives the opportunity toinvestigate the group properties in more detail. We report the discoveryof 26 new members of the group and the confirmation of 18 candidatesfrom the literature. This almost triples the number of known lambdaBootis stars. The existence of one member in the young open cluster NGC2264 and four members in the Orion OB1 association proves that thelambda Bootis phenomenon already works at very early stages of stellarevolution. Recent results from the Hipparcos mission have shown that thewell established lambda Bootis stars of the Galactic field comprise thewhole area from the Zero Age Main Sequence to the Terminal Age MainSequence (~ 109 yr for an A-type star). There is a continuoustransition between very young and rather evolved evolutionary stages. Wefind that the overall percentage of lambda Bootis type among all normaltype stars in the spectral range from B8 to F4 is 2% in the Galacticfield as well as in open clusters. Furthermore, 44 metal-weak objectsare listed which might be connected with the lambda Bootis phenomenon.Our biased sample (chosen by photometric boxes) is not distinguishedfrom all A-type stars in the corresponding spectral region by therotational velocity distribution. Only for the luminosity classes IV andIII (especially for the cooler program stars) the determined mean v sini values are very high compared to those of the literature. Based onobservations from the Observatoire de Haute-Provence, OsservatorioAstronomico di Padova-Asiago, Observatório do Pico dosDias-LNA/CNPq/MCT, Chews Ridge Observatory (MIRA) and University ofToronto Southern Observatory (Las Campanas).
| uvby light curves of the eclipsing binary system V2154 Cyg
This paper presents complete uvby light curves for the recentlydiscovered eclipsing binary system V2154 Cyg. Additional CrawfordHbeta data were also obtained. Three times of primary minimaand two secondary minima are determined. An improved orbital period isfound to be 2\fd6306312. A detailed photometric analysis is made usingthe EBOP code. This eclipsing binary is probably one of the componentsof a much wider double star, forming altogether a triple system. Theresults show that the eclipsing pair is a detached system with twolate-type stars very different in size. Masses of about M_1=1.4Msun and M_2=0.8 Msun are inferred for thecomponents by using stellar evolution models. The total mass of theprobable triple system is estimated to be of about 3.5 Msun,leading to a minimum orbital period of about 140 yr for the visual pair.Table 1 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr ( 130.79.128.5)} or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/372/588
| The IMF of open star clusters with Tycho-2
We studied the fields of nine nearby open star clusters based on theTycho-2 catalogue. We determined membership probabilities for the starsin the cluster fields from the stellar proper motions and used theTycho-2 photometry to compute the initial mass function (IMF) of theclusters from the main sequence turn-off point down to approx. 1 M_sun.We found IMF slopes ranging from Gamma =-0.69 down to Gamma =-2.27 (whenthe Salpeter \cite{salpeter} value would be Gamma =-1.35). We alsostudied the membership of individual stars of special astrophysicalinterest. In some cases previous results had to be revised. As aby-product, we investigated some general properties of the Tycho-2catalogue; we confirmed that the Tycho-2 proper motions show onlymarginal deviations from the Hipparcos catalogue. On the other hand, insome regions the completeness of the catalogue seems to decrease atmagnitudes brighter than claimed by Høg et al. (\cite{tycho2}).Based on observations of the ESA Hipparcos satellite.
| delta Scuti and related stars: Analysis of the R00 Catalogue
We present a comprehensive analysis of the properties of the pulsatingdelta Scuti and related variables based mainly on the content of therecently published catalogue by Rodríguez et al.(\cite{retal00a}, hereafter R00). In particular, the primaryobservational properties such as visual amplitude, period and visualmagnitude and the contributions from the Hipparcos, OGLE and MACHOlong-term monitoring projects are examined. The membership of thesevariables in open clusters and multiple systems is also analyzed, withspecial attention given to the delta Scuti pulsators situated ineclipsing binary systems. The location of the delta Scuti variables inthe H-R diagram is discussed on the basis of HIPPARCOS parallaxes anduvbybeta photometry. New borders of the classical instability arepresented. In particular, the properties of the delta Scuti pulsatorswith nonsolar surface abundances (SX Phe, lambda Boo, rho Pup, delta Deland classical Am stars subgroups) are examined. The Hipparcos parallaxesshow that the available photometric uvbybeta absolute magnitudecalibrations by Crawford can be applied correctly to delta Scutivariables rotating faster than v sin i ~ 100 km s{-1} withnormal spectra. It is shown that systematic deviations exist for thephotometrically determined absolute magnitudes, which correlate with vsin i and delta m1. The photometric calibrations are found tofit the lambda Boo stars, but should not be used for the group ofevolved metallic-line A stars. The related gamma Dor variables and thepre-main-sequence delta Scuti variables are also discussed. Finally, thevariables catalogued with periods longer than 0fd 25 are examined on astar-by-star basis in order to assign them to the proper delta Scuti, RRLyrae or gamma Dor class. A search for massive, long-period delta Scutistars similar to the triple-mode variable AC And is also carried out.
| Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Open clusters with Hipparcos. I. Mean astrometric parameters
New memberships, mean parallaxes and proper motions of all 9 openclusters closer than 300 pc (except the Hyades) and 9rich clusters between 300 and 500 pc have been computed using Hipparcosdata. Precisions, ranging from 0.2 to 0.5 mas for parallaxes and 0.1 to0.5 mas/yr for proper motions, are of great interest for calibratingphotometric parallaxes as well as for kinematical studies. Carefulinvestigations of possible biases have been performed and no evidence ofsignificant systematic errors on the mean cluster parallaxes has beenfound. The distances and proper motions of 32 more distant clusters,which may be used statistically, are also indicated. Based onobservations made with the ESA Hipparcos astrometry satellite
| Search for star clustering: methodology and application to the Two Micron Galactic Survey
A new approach to the study of the large-scale stellar clusterdistribution in the Galaxy based on two-point correlation techniques ispresented. The basic formalism for this method is outlined, and itsapplications are then investigated by the use of a simple model ofcluster distribution in the Galaxy. This provides an estimate of thepotentials of the two-point correlation function for indicatingclustering in the measured star positions, which can be related to thepresence of star clusters in the observed field. This technique is thenapplied to several areas of the Two Micron Galactic Survey catalogue,from which information is obtained on the distribution of clustersaccording to position in the Galaxy, as well as about age, density ofstars, etc.
| A report on the studies of star clusters with the UPSO 104-cm Sampurnanand telescope during last 25 years
Not Available
| Baldone Schmidt Telescope Plate Archive and Catalogue
The article presents information on the archive and catalogue of theastrophotos taken with the Schmidt telescope of the Institute ofAstronomy of the University of Latvia (until July 1, 1997 --Radioastrophysical Observatory of the Latvian Academy of Sciences) inthe period 1967--1998. The archive and catalogue contain more than 22000direct and 2300 spectral photos of various sky regions. Information onthe types of photo materials and color filters used as well as on mostfrequently photographed sky fields or objects is given. The catalogue isavailable in a computer readable form at the Institute of Astronomy ofthe University of Latvia and at the Astrophysical Observatory in Baldone(Riekstukalns, Baldone, LV-2125, Latvia), e-mail: astra@latnet.lv.
| A Search for Star Clusters from the HIPPARCOS Data
We present results of a search for nearby star clusters and associationsusing Hipparcos Catalogue data, restricting the sample to stars withparallaxes above 2 mas (d <~ 500 pc). Two new OB associations havebeen identified in the Carina-Vela and Cepheus-Cygnus-Lyra-Vulpecularegions. A very probable new open cluster has been discovered in Carina.The cluster, a Car, named after its brightest member, is young (60 Myr)and nearby (d = 132 pc). However, only seven bona fide members can bedrawn from the Hipparcos data. We report a detection of nine opencluster candidates in the distance range of 150 to 400 pc, and sixpossible associations almost all located within the Gould belt, althoughslightly older than the known nearby associations. In all cases, wepresent Yale theoretical isochrone fits to the color-magnitude diagrams,which indicate a moderate spread of ages between 60 to 200 Myr.Evidently, these young open cluster and association candidates arerelated to the overall distribution of young OB and A-type stars in thesolar neighborhood.
| Radial velocities and binarity in open clusters
Not Available
| Cluster membership determinations from proper motion surveys
Not Available
| Thirty years of research with the Baldone Schmidt Telescope
We describe the research done with the Baldone Schmidt telescope(80/120/240 cm) of the Radioastrophysical Observatory. The telescope hastwo objective prisms with reciprocal dispersions of 600 and 1130 A/mm atH-gamma. One of the main research projects is the search for andphotometric study of galactic carbon stars. The telescope has also beenused for novae studies in M 31 and stellar photometry in open clustersand fields of special interest. Comet studies, particularly during theInternational Halley Watch, proved to be another successful applicationof the telescope. The archive of the Baldone Schmidt telescope containsnearly 20,000 direct and 2000 spectral plates and films.
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